The perception of gloss: A comparison of three methods for studying intentionally polished bone tools

Abstract

Polished bone and stone tools are well known from many archaeological contexts. In use-wear studies, polish is usually characterised by the degree of surface roughness, or more subjectively by its visual appearance. Visual appearances, however, may be deceptive, and the scale of analysis of traditional surface roughness studies is often too fine to consider the overall visual effect of a polished surface. Here I consider three techniques for characterising modified bone surfaces and assess the correlation between surface roughness and gloss. My results show that softer contact materials generally produce higher gloss values than harder materials, but within these two broad categories results are more complex. Based on these experimental results a trial assessment is presented of archaeological bone tools from assorted Holocene sites. The ability to perceive and appreciate polished surfaces is linked to developments in the superior temporal sulcus region of the human brain, which is the same region in which our ability to perceive shapes and colour developed. Deliberately polished bone tools from Pleistocene contexts therefore have the potential to provide insights into cognitive developments in our species. The specular reflectance or gloss of a polished surface provides a quantifiable and repeatable measure, more suitable than surface roughness analysis, for characterising deliberate polish, although a combined approach is advocated.